Air Filter Element, Filter Housing and Filter Arrangement

ABSTRACT

An air filter element ( 10 ) with a cylindrical central pipe ( 11 ) is provided wherein at one end of the central tube ( 11 ) a device ( 18 ) for transmission of torque from a tool to the air filter element ( 10 ) is provided and at the other end of the central tube ( 11 ) a fastening device ( 14 ) for detachably mounting the filter element ( 10 ) within a cylindrical support body ( 21 ) by means of an insertion/rotation movement is provided.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 13/524,477,filed Jun. 15, 2012, claiming a priority date of Jun. 15, 2011 based onprior filed German patent application No. 10 2011 106 503.6.

TECHNICAL FIELD

The present invention concerns a filter element for filtering air, ahousing for such a filter element, as well as a filter arrangement withsuch a filter element and housing.

BACKGROUND OF THE INVENTION

Filter elements are used for filtering fluid flows or gaseous media. Forexample, they are used for filtering an air flow that is guided into apassenger compartment of a motor vehicle. For this purpose, they can beused in particular in an air-conditioning device mounted in a motorvehicle in order to clean ambient air from health-hazardous substances,odors or the like. Examples of such filters are particle filters, odorfilters or combinations thereof. A further field of use of filterelements is air filters that remove suspended particles from the airthat is supplied to an internal combustion engine. Generally, such airfilters have a housing in which an exchangeable air filter element isprovided.

U.S. Pat. No. 4,588,426 discloses an air filter with a filter housinghaving at its bottom several vertically arranged rods. A filter elementcan be pushed onto the rods and the filter housing can be closed by acover. The cover is screw-connected by means of a wing bolt that extendsto the bottom of the filter housing. The exchange of the filter elementcan be realized thus in a simple way because the cover can be removed bysimply releasing the wing bolt and the filter element can be exchangedby hand without this requiring an additional tool. However, it is oftendesirable that such a simple exchange without tool is actually not madepossible because it carries the risk that the filter element isexchanged by the consumer in an inappropriate way or by a using wrongfilter element. This, in turn, can cause an insufficient filteringaction or can cause the filter material to wear faster.

WO 00/56423 A1 discloses an air filter with two cup-shaped housingshells that are detachably connected to each other, wherein the lowerone of the shells has a conical support pipe integrated therein. Ontothis support pipe, a conical round filter element is pushed andsubsequently the top housing shell is placed onto the lower housingshell and is screw-connected with one end of the support pipe. In thisair filter the housing shells are screw-connected to each other so thata release without tool is not possible, but the screw connection can berealized by a screwdriver so that here there is also the risk ofimproper exchange of the filter element with the aforementioneddisadvantages.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an improved air filterelement, a filter housing for such a filter element as well as a filterarrangement that are of a simple configuration and can be producedeasily and, at the same time, ensure that the filter element received inthe filter housing cannot be exchanged, or exchanged only withdifficultly, without a tool, in particular a special tool.

Accordingly, an air filter element is provided with a cylindricalcentral tube wherein at one end of the central tube a torquetransmission device for transmitting torque from a tool onto the airfilter element is provided and at the other end of the central tube afastening device for detachably mounting the filter element in acylindrical support body by means of an insertion/rotation movement isprovided.

Examples for connections by means of an insertion/rotation movement arescrew connections, bayonet connections, locking connection and/or snapconnections. An advantage of insertion/rotation connections compared toinsertion/locking connections is that they release less easily as aresult of vibrations which is advantageous in particular for use intrucks, construction machinery, agricultural machines and the like. Theinstalled air filter element cannot be removed, or removed only withdifficulty, by hand from the support body because it is received in thesupport body and therefore its outer circumference is covered by thesupport body. In this way, the support body can provide in particularalso a mechanical protection of the filter element with respect todamages. This can be important in particular in connection with portabledevices where a stable positioning of the device during filter exchangecannot always be ensured and therefore the risk of damage of filterelements exists when the devices drop to the ground with the filterhousing being open. The combination of fastening means with the torquetransmission device provides a filter element which by means of a toolcan be attached to and removed from a support body with a simplemovement but, without a tool, can be attached or released only withdifficultly.

With an appropriate configuration of the tool, it is sufficient fortransmission of torque when at the end of the filter element a sectionis provided as a torque transmission device that is not of rotationalsymmetry. The torque transmission device can be designed relative to thecylinder axis of the central tube as a projection or recess that is notof rotational symmetry. For example, on a cover that closes off thecentral tube a polygonal recess can be provided or beads or projectionson the cover can be provided that enable a screwing-in action by meansof a tool.

At one end of the central tube an end disk can be provided that has atub-shaped recess that is provided at its bottom with the torquetransmission device. In this context, a tub-shaped recess is to beunderstood as a recess of a blind bore shape having a diameter that isgreater than its depth. The torque transmission device can be designedin particular as a projection that rises from the bottom of the recessin the end disk but is positioned below the upper rim of the end disk.The projections that are provided in the recess of the end disk serve asmeans of transmitting torque of a tool especially designed for this.Because these projections are provided in a recess, they are notsuitable for unscrewing or removing the air filter element by hand fromthe support body. In this way, it can be ensured that the air filterelement cannot be removed, or removed only with difficulty, from thesupport body without a special tool, and an improper exchange of the airfilter element can be prevented. The tub-shaped recess, when viewed fromabove, can be of a circular shape; this facilitates the use of the tool.

The lateral surfaces of the projections can define a substantially rightangle, i.e., an angle of 75 to 105 degrees with the bottom surface ofthe recess. Moreover, the recess, when viewed from above, can becircular. The lateral surfaces of the projections can substantiallyextend in radial direction from the rim of the recess in the directiontoward the cylinder axis of the central tube. Accordingly, a largecontact surface between the special tool and the projections can beensured and sliding off of the special tool from the projections can beavoided.

The air filter element can be provided, for example, with at least twoprojections. The projections can moreover be provided opposite eachother on the rim of the recess. Accordingly, relatively shortprojections can be used as means of transmitting torque of a specialtool; this makes a removal of the air filter element by hand even moredifficult.

For example, the length of the lateral surfaces of the projectionsextending in radial direction can be less than half the radius of therecess. The projections can be provided, for example, so as to belocated opposite to each other on the rim of the recess. This enables anefficient transmission of torque onto the air filter element.

The end disk and the central tube can be monolithically configured. Thisenables a simple and inexpensive manufacture of the filter elementwithout additional seals, for example, by injection molding.

Accordingly, a filter housing for receiving the above described airfilter element is provided that comprises a housing top part and ahousing bottom part that is detachably connected to the housing toppart, wherein on the housing bottom part an air-permeable cylindricalsupport body is provided that has at its end that is facing the housingbottom part housing-associated fastening means interacting with thefilter-associated fastening devices of the air filter element forattachment of the air filter element by means of an insertion/rotationmovement.

The housing bottom part can be configured monolithically together withthe cylindrical support body. This provides, on the one hand, a greaterpressure resistance and ensures, on the other hand, improved handlingduring installation or removal. Moreover, the filter housing can thus beproduced in a simple and inexpensive way.

The cylindrical support body can be designed as an air-permeable gridstructure. This provides a relatively high stability of the support bodywherein the relatively large outer surface of the support body can beused for the air flow through the filter.

The two housing shells (housing top part and housing bottom part) can beheld together, for example, by means of a buckle or a detachable screwconnection.

In one embodiment, for opening the housing, the housing top part can bepivoted and folded open about a pivot bearing that is arranged betweenhousing top part and housing bottom part so that the support pipebecomes accessible.

In one embodiment, an air inlet opening for a cyclone filter stage isprovided in particular laterally on the housing top part and/or thehousing bottom part. The cyclone filter stage is preferably integratedas a preseparator into the housing part or parts. The cyclone filterstage is in particular formed by means of at least one inline cyclonecell that comprises a pipe provided with an inlet-side deflection meansfor imparting a rotational movement to the air flow and an outlet-sideimmersion pipe for separating the radially outwardly located flow areaswith higher particle proportion as well as a discharge opening fordischarging the thus separated particles. The cyclone filter stage isarranged especially preferred such that the flow exiting from it is notdirectly oriented onto a filter element but flow past it. In this way, amore uniform loading of the filter element can be achieved. It isfurther preferred that the flow that is exiting from the cyclone filterstage can flow past the second filter element and can be directed onto ahousing wall that is positioned opposite the cyclone filter stage. Thiscan also contribute to a more uniform inflow at the filter elements, inparticular when only a minimal number of inline cyclones are used as acyclone filter stage.

In one embodiment of this filter arrangement, the filter element iscompletely received with positive fit in the support body. For such acomplete reception of the filter element in the support body, thesupport body surrounds the filter element externally so that the upperend of the filter element is positioned below the top edge of thesupport pipe. Accordingly, the upper end of the filter element does notproject from the support pipe so that the upper end of the filterelement also cannot be gripped by hand and removal without a tool is notpossible or possible only with difficulty.

In a further embodiment of the filter arrangement, a second cylindricalfilter element is provided moreover. The second filter element haspreferably a zigzag-shaped folded filter bellows of a fibrous filtermedium that is closed to a ring. The support body forms in particular acentral tube of the second cylindrical filter element so that a radialsupport of the filter bellows relative the interior can be ensured.Accordingly, a multi-stage filtration can be realized wherein the secondfilter element is preferably flowed through first from the exterior (rawside) to the interior (clean side) and serves as a main filter elementfor filtration of relatively large particles and the first filterelement as a secondary filter element serves for filtration ofrelatively small particles. In this connection, the first filter elementcan be secured by means of an insertion/rotation movement. The secondfilter element can be configured to be pushed onto the support body.When the support body forms a central tube of the second filter element(main filter element), this second filter element can be of a simplerconfiguration because it must not have its own central tube. The secondfilter element can be designed to be pushed onto the first filterelement or the support body, i.e., can be mounted and removed without atool. Preferably, the second filter element has an end disk with anoutflow opening and a seal which serves for sealing relative to thefirst filter element or the support body. This seal is preferablydesigned as a radial seal that is of an annular configuration and canengage a cylindrical sealing surface of the first filter element or thesupport body such that the raw side is separated from the clean side. Itis further preferred that the second filter element has a second closedend disk.

Further possible implementations of the invention comprise alsocombinations that are not explicitly described of features or embodimentvariants described above or in the following in respect to theembodiments. In this connection, a person of skill in the art will alsoadd individual aspects as improvements or supplements to the respectivebasic form of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying Figures, where like reference numerals refer toidentical or functionally similar elements throughout the separate viewsand which together with the detailed description below are incorporatedin and form part of the specification, serve to further illustratevarious embodiments and to explain various principles and advantages allin accordance with the present invention.

Features of the present invention, which are believed to be novel, areset forth in the drawings and more particularly in the appended claims.The invention, together with the further objects and advantages thereof,may be best understood with reference to the following description,taken in conjunction with the accompanying drawings. The drawings show aform of the invention that is presently preferred; however, theinvention is not limited to the precise arrangement shown in thedrawings.

FIG. 1 is a perspective view of a filter arrangement, consistent withthe present invention;

FIG. 2 is a perspective view of a filter element as well as of a bottomhousing shell in which the filter element is installed, consistent withthe present invention;

FIG. 3 is a sectioned view of the filter element and of the housingshell of FIG. 2;

FIG. 4 is a detail view of the connection of the filter element with thehousing shell;

FIG. 5 is a perspective view of the bottom housing shell of the filterhousing; and

FIG. 6 is a perspective view of a bottom housing shell and a main filterelement of a filter arrangement.

In the Figures the same or functionally the same elements, if nothingelse is indicated, are provided with the same reference characters.

Skilled artisans will appreciate that elements in the figures areillustrated for simplicity and clarity and have not necessarily beendrawn to scale. For example, the dimensions of some of the elements inthe figures may be exaggerated relative to other elements to help toimprove understanding of embodiments of the present invention.

DETAILED DESCRIPTION

Before describing in detail embodiments that are in accordance with thepresent invention, it should be observed that the embodiments resideprimarily in combinations of apparatus components related to a filterelement for filtering air, a housing for such a filter element, as wellas a filter arrangement. Accordingly, the apparatus components have beenrepresented where appropriate by conventional symbols in the drawings,showing only those specific details that are pertinent to understandingthe embodiments of the present invention so as not to obscure thedisclosure with details that will be readily apparent to those ofordinary skill in the art having the benefit of the description herein.

In this document, relational terms such as first and second, top andbottom, and the like may be used solely to distinguish one entity oraction from another entity or action without necessarily requiring orimplying any actual such relationship or order between such entities oractions. The terms “comprises,” “comprising,” or any other variationthereof, are intended to cover a non-exclusive inclusion, such that aprocess, method, article, or apparatus that comprises a list of elementsdoes not include only those elements but may include other elements notexpressly listed or inherent to such process, method, article, orapparatus. An element preceded by “comprises . . . a” does not, withoutmore constraints, preclude the existence of additional identicalelements in the process, method, article, or apparatus that comprisesthe element.

The invention will be explained in the following with the aid of afilter for the combustion air of an internal combustion engine, forexample, a motor vehicle. Instead of being designed for filtering air,corresponding filter elements can be designed, for example, forfiltering another gaseous or even liquid medium, for example, oil.

In the following, with the aid of FIGS. 1 to 5, a filter arrangement 1with a filter element 10 according to one embodiment is disclosed. FIG.1 is a perspective view of a filter arrangement 1. FIG. 2 is aperspective view of bottom housing shell 20 a of a fluid-tight housing20 of the filter arrangement in which the filter element 10 isinstalled. FIG. 3 is a sectioned view of the filter element 10 and ofthe housing shell 20 a in FIG. 2. FIG. 4 shows in a detail view theconnection of the filter element 10 with the housing shell 20 a. FIG. 5is a perspective view of the bottom housing shell 20 a of the filterhousing 20.

It should be noted that the expressions “top” and “bottom” relate inthis context to the orientation in the Figures and not necessarily tothe orientation of the filter arrangement 1 in the mounted state.

The filter arrangement 1 of this embodiment embodied as an air filterhas a filter element 10 (compare FIGS. 2 to 4) which is received in afilter housing 20 of plastic material or the like. The filter housing 20has a bottom housing shell 20 a with a support 21 and a top housingshell 20 b.

The two housing shells 20 a and 20 b can be held together by means of abuckle 22. When the buckle 22 is open, the housing shell 20 b can bepivoted and folded open about a pivot bearing 23 that is provided at theupper end of the rear wall of the bottom housing shell 20 a so that thesupport tube 21 is accessible. In the support tube 21, in the way to bedescribed in detail below, the filter element 10 is received andsecured.

An air inlet opening 24 for a cyclone filter stage 25 is providedlaterally at the top housing shell 20 b. The cyclone filter stage 25 isintegrated into the top housing shell 20 b. Through the air inletopening 24, the air from which the particles are to be removed byfiltering is conveyed into the cyclone filter stage 25. In the cyclonefilter stage 25, particles are first separated from the air by means ofcyclone separation. The particles can be removed by means of a dischargeopening 26. The cyclone filter stage is in particular formed by at leastone inline cyclone that is provided with a pipe having deflection meansat the inlet side for imparting a rotational movement to the air flowand an outlet-side immersion pipe for separation of radially outwardlylocated flow areas with higher particle proportion. The cyclone filterstage is arranged particularly preferred such that the flow exiting fromit is not oriented directly onto a filter element but flows past it. Inthis way, a more uniform loading of the filter element can be achieved.It is further preferred that the flow that is exiting from the cyclonefilter stage flows past the second filter element and is directed onto ahousing wall that is positioned opposite the cyclone filter stage. Thiscan also contributed to a more uniform inflow at the filter elements, inparticular when only a minimal number of inline cyclones are used as acyclone filter stage.

The thus pre-cleaned air then passes through the filter element that isprovided in the support pipe 21 and is purified by the filter materialprovided therein. The purified air leaves the housing finally through anair outlet socket 27 (compare FIG. 4) at the bottom of the bottomhousing shell 20 a below the support pipe 21. The purified air can besupplied to an internal combustion engine of a motor vehicle or thelike.

As can be seen in particular in FIG. 3, the filter element 10 comprisesa cylindrical central tube 11 whose cylindrical outer surface issurrounded by a filter material 12 attached by a first seal 13 on theupper end of the central tube 11. The filter element 10 is fitted intothe support pipe 21. The support pipe 21 is a cylindrical grid-shapedsupport body which is formed monolithically with the bottom housingshell 20 a. The lower end of the support pipe 21 adjoins in thisconnection a cup-shaped section of the bottom housing shell 20 a that isformed at the bottom of the bottom housing shell 20 a so that the filterarrangement 1 is provided with greater stability.

At its lower end, the central tube 11 has fastening means for fasteningthe filter element 10 at the housing shell 20 a. This fastening means atthe filter is formed in the illustrated embodiment as a thread 14.Between the thread 14 and the filter material 12 a second seal 15 isarranged. The fastening means at the filter interact with fasteningmeans at the housing in order to secure the filter element 10 in thesupport pipe 21. More precisely, at the housing at the lower end of thesupport pipe 21 a thread 29 is provided. The filter element 10 can thusbe secured in the support pipe 21 by means of an insertion/rotationmovement. In this connection, it is first pushed in axial direction intothe support pipe 21 until the filter-associated thread 14 rests on thehousing-associated thread 29. By rotation of the filter element 10, thefilter element 10 is screw-connected to the support pipe 21. The threads14 and 29 must not be provided about the entire circumference of thecentral tube 21 or the support tube 21 but can also be formed as severalsection-wise projections along the circumference. In particular, thethreads 14 and 29 can be formed such that the filter element 10 byrotation about a relatively small angle, for example, an angle notgreater than 90 degrees or not greater than 45 degrees, can be securedin the support pipe 21. In this way, a fast fixation of the filterelement 10 is possible. Instead of the above described screw connection,the filter element 10 can be secured also by means of a bayonet, lockingand/or snap connection in the support pipe 21. Even for suchconnections, the filter element 10 is secured by an insertion/rotationmovement in the support pipe 21.

At the upper end of the central tube 11, an end disk 16 is provided thatcloses off air-tightly the central tube 11. In the illustratedembodiment, the central tube 11 and the end disk 16 are of a monolithicconfiguration but it is also possible to provide the end disk as aseparate element. In the end disk 16 the tub-shaped recess 17 isprovided that, in the illustrated embodiment, has the shape of anupside-down circular truncated cone. The end disk 16 has a first annularsection 16 a that adjoins the cylindrical wall of the central tube 11and extends at a right angle thereto radially in inward direction. Asecond annular section 16 b adjoins the inner end of this annularsection 16 a and defines together with the first annular section 16 a anangle of, for example, 110 to 160 degrees, for example, approximately135 degrees. A disk-shaped third section 16 c adjoins this secondsection 16 b and forms together with the second section 16 b the recess17. The first seal 13 is also of an annular shape and surrounds thefirst section 16 a of the end disk as well as the end of the filtermaterial 12 that is placed thereon so that the filter material 12 issecured at the end of the central tube 11. Foam of polyurethane (PU) orPUR foam can be used as a material for the first seal 13.

The air filter element 10 is provided with a torque transmission devicefor transmitting torque from a tool onto the air filter element. Forthis purpose, at the inner rim of the recess 17, i.e., at the locationwhere the second section 16 a meets the third section 16 c, at least oneprojection 18 extending in radial direction is provided. In theillustrated embodiment, as a torque transmission device two projections18 a and 18 b are provided which extend from the rim of the recess 17 toa location that is approximately at the center between the rim of therecess 17 and the center of the end disk 16. These projections 18 a and18 b form projections that project from the bottom of the recess 17 upto a height that is below the upper rim of the end disk 16. In theembodiment illustrated in FIG. 2, the two projections 18 a and 18 b aresubstantially of a parallelepipedal shape and are positioned at opposedlocations of the rim, i.e., displaced by an angle of 180 degrees.

By means of the projections 18 a and 18 b, the filter element 10 can bemounted on or removed from the support pipe 21. For mounting, the filterelement 10 is pushed in the afore described way into the support pipe 21until the threads 14 and 29 rest on each other. With a special tool thatis not disclosed in detail, the filter element 10 can now be turned andsecured. For this purpose, the special tool is inserted into the recess17 and turned so that it is laterally forced against the lateralsurfaces of the projections 18 a and 18 b. The projections 18 a and 18 babsorb the torque of the special tool and transmit the torque to thefilter element 10. There is no limitation with regard to theconfiguration of the special tool, aside from the limitation that itmust be suitable to transmit torque to the projections 18 a and 18 b.For example, at the end of the special tool a rectangular blade, similarto that of a screwdriver, can be provided. However, it is also possiblethat the shape of the special tool is matched to the recess 17, i.e.,has the shape of a truncated cone with recesses for the projections 18.

When, for example, in connection with maintenance, the filter element 10is to be released from the support pipe 21, the special tool is requiredalso for this purpose. In the state in which it is completely receivedin the support pipe 21, the filter element 10 is surrounded by thegrid-shaped support pipe 21 so that it cannot be gripped by hand andunscrewed. On the upper end, there is also no point of attack withwhich, without a tool, torque can be transmitted onto the filter element10. Accordingly, the filter element 10 cannot be secured in or releasedfrom the support pipe 21 by hand, or secured and released only withdifficulty. In this way, a proper exchange of the filter element 10 isensured because the required special tool in general is available onlyat authorized repair shops or dealerships or to appropriately authorizedor trained maintenance personnel.

The lateral surfaces of the projections 18 define an angle of, forexample, 75 to 105 degrees and preferably substantially 90 degreesrelative the bottom of the recess. The lateral surfaces of theprojections 18 extend substantially in radial direction from the rim ofthe recess 17 in the direction of the cylinder axis of the central tube11. Accordingly, a large contact surface between the special tool andthe projections 18 can be ensured and sliding off of the special toolfrom the projections 18 is avoided. Moreover, by providing theprojections 18 at the rim of the recess, i.e., removed as far aspossible from the axis of rotation, an efficient torque transmission isensured.

The filter housing 20 of this embodiment can be opened and closedwithout a tool. The buckle closure enables in this connection a fastone-hand operation. Since the support pipe 21 is of a grid-shapedconfiguration and extends up to the end of the filter element 10, it isnot possible to mount and remove the filter element 10 without a tool,as described above. Accordingly, a special tool for mounting andremoving the filter element 10 is required; this ensures propermaintenance work. However, this can be done with a few manipulationsbecause the filter housing 20 can be opened with one hand and the filterelement 10 can be secured with a simple insertion/rotation movement.

In the illustrated embodiment, two projections 18 are provided but it isalso possible to have more than two projections 18. Also, it is possibleto provide only a continuous projection that extends from the rim on oneside across the center of the end disk 16 up to the opposite rim of therecess 17. Moreover, it is also possible to provide the two projections18 a and 18 b not opposite each other but, for example, at an angle of90 degrees along the rim of the recess 17. This requires an appropriateconfiguration of the special tool and prevents that it can be replacedby a single rectangular blade or the like.

The filter arrangement 1 that comprises the filter housing 20 and thefilter element 10 effects a two-stage filtration with a cycloneprefiltering action with the cyclone filter stage 21 and a mainfiltering action with the filter element 10. It is however also possibleto provide more filter stages. Such a filter arrangement 50 isschematically illustrated in FIG. 6.

The filter arrangement 50 according to this embodiment has the abovedescribed filter housing 20, a secondary filter element that is notshown in more detail, as well as a main filter element 60. The abovedescribed filter element 10 can be employed as a secondary filterelement so that aspects of the filter housing 20 and the filter element10 that have already been discussed will not be explained again in thiscontext. FIG. 6 shows only the bottom housing shell 20 a of the filterhousing 20 as well as the second filter element 60 that is pushed ontothe support pipe 21.

In the illustrated arrangement, the filter element 60 serves as a mainfilter element of a filter arrangement 50 that comprises the main filterelement 60 and the secondary filter element. The main filter element 60is also cylindrical and comprises a cylindrical grid-shaped centraltube, not illustrated in detail, that is enveloped by a filter material61. At the end of the central tube an end disk 62 of polyurethane (PU)or PUR foam is provided which closes off the cylindrical central tubeair-tightly.

The filter material 61 of the main filter element 60 is designed forfiltering out larger particles and the filter material of the secondaryfilter element is designed for filtering out finer particles from theair.

After prefiltration with the cyclone filter stage 25 the air to befiltered passes through the filter material 61 of the main filterelement 60, passes through the support pipe 21, and penetrates then thefilter material of the secondary filter element in order to then beguided outwardly through the air outlet opening at the bottom of thebottom housing shell 20 a. Accordingly, a three-stage filtration isprovided.

The main filter element 60 can be pushed into and removed from thesupport pipe 21 by hand with a simple movement so that the exchange canbe done quickly and simply. In this connection, because of theconfiguration of the secondary filter element in the above describedway, it is ensured that for complete exchange of the filter arrangementa special tool is required so that proper maintenance is ensured.

In an advantageous embodiment, the support pipe 21 can servesimultaneously as a central pipe of the main filter element 60.Accordingly, an additional component can be avoided which enables aneven more cost-efficient realization of the filter arrangement.

The above described embodiment is only to be understood as an exemplaryone and other configurations are conceivable that are also meant to beencompassed by the scope of protection. For example, the torquetransmission device can also be provided in the end disk as a polygonalrecess that has no rotation symmetry. Moreover, it is also possible thatas a torque transmission device several recesses are provided in the enddisk. Moreover, it is possible that the torque transmission device isdesigned as a projection or projections on the end disk that has/have norotational symmetry. With these or other geometries, it can also beensured that the torque transmission device interacts in accordance withthe key-and-lock principle with a tool and, without it, cannot bemounted or only mounted with difficulty.

In the foregoing specification, specific embodiments of the presentinvention have been described. However, one of ordinary skill in the artappreciates that various modifications and changes can be made withoutdeparting from the scope of the present invention as set forth in theclaims below. Accordingly, the specification and figures are to beregarded in an illustrative rather than a restrictive sense, and allsuch modifications are intended to be included within the scope of thepresent invention. The benefits, advantages, solutions to problems, andany element(s) that may cause any benefit, advantage, or solution tooccur or become more pronounced are not to be construed as a critical,required, or essential features or elements of any or all the claims.The invention is defined solely by the appended claims including anyamendments made during the pendency of this application and allequivalents of those claims as issued.

We claim
 1. An filter air filter element (10) comprising: a cylindricalcentral tube (11); an end disk (16) formed monolithically in one-pieceas a unitary component with the cylindrical central tube (11) andclosing off a first axial end of the cylindrical central tube (11) andcovering an axial end face of the filter element; a filter material (12)arranged on and covering a cylindrical outer surface of the cylindricalcentral tube (11); a torque transmission device (18) formed on the enddisk (16) of the central tube (11), the torque transmission deviceoperable to transmit torque from a tool to the air filter element (10);a fastening device (14) formed on or secured onto an opposing secondaxial end of the central tube (11), the fastening device (14) operableto detachably secure the filter element (10) into an interior of acylindrical support body (21) arranged in an interior of the filterhousing, the cylindrical support body (21) cylindrically surrounding aradial exterior of the air filter element, the detachable securingaccomplished by an insertion/rotation movement of the fastening devicerelative to the filter housing.
 2. The air filter element according toclaim 1, wherein the torque transmission device (18) is formed as aprojection or recess that has no rotational symmetry relative to thecylinder axis of the central tube (11).
 3. The air filter elementaccording to claim 1, wherein the end disk includes an inwardly recessedtub-shaped recess (17); wherein the torque transmission device isarranged at and formed on or secured to a bottom of the tub-shapedrecess.
 4. The air filter element according to claim 1, wherein thetorque transmission device (18) includes at least two projections thatare provided, positioned opposite each other, on a rim of the recess(17).
 5. The air filter element according to claim 2, wherein the enddisk includes a rim surrounding an inwardly recessed tub-shaped recess(17) spaced axially inwardly from the rim; wherein the torquetransmission device (18) includes at least two projections that areprovided, positioned opposite each other, on a rim of the recess (17),the at least two projections projecting axially outwardly away from thefilter element, the at least two axial projections arranged on a bottomof the tub-shaped recess.
 6. The air filter element according to claim1, wherein the end disk (16) entirely covers an axial end face of thefilter element.
 7. The air filter element according to claim 5, whereinan annular first seal (13) is arranged on an axially outer side of therim of the end disk (16) and on an axial end of the filter material(12); wherein the annular first seal (13) secures the filter material(12) onto the central tube.
 8. A filter housing (20) for receiving anair filter element according to claim 1, the filter housing comprising:a top housing part (20 b); a bottom housing part (20 a) detachablysecured to the top housing part (20); wherein the filter elementaccording to claim 1 is arranged within the filter housing; wherein thebottom housing part has an air-permeable cylindrical support body (21)secured to the housing in an interior of the filter housing, thecylindrical support body having an end arranged at and facing aninterior of bottom housing part (20 a); a housing associated fasteningdevice (24) secured to the bottom housing part and within a radialinterior of the bottom housing part air-permeable cylindrical supportbody (21); wherein the cylindrical support body (21) cylindricallysurrounds a radial exterior of the air filter element (10); wherein thehousing associated fastening device (24) interacts with and engages witha filter-associated fastening device (14) of the air filter element forfastening the air filter element (10) by means of an insertion/rotationmovement.
 9. The filter housing according to claim 8, wherein the bottomhousing part (20 a) is monolithically formed together with thecylindrical support body (21) as a one-piece unitary component.
 10. Thefilter housing according to claim 8, wherein the cylindrical supportbody (21) is formed as an air-permeable grid.
 11. A filter arrangementfor a portable hand-held power tool, with an air filter element (10)according to claim 1, which is mounted in a filter housing (20),comprising: the air filter element (10) according to claim 1; the filterhousing comprising: a top housing part (20 b); a bottom housing part (20a) detachably secured to the top housing part (20); wherein the filterelement according to claim 1 is arranged within the filter housing;wherein the bottom housing part has an air-permeable cylindrical supportbody (21) secured onto the interior of the bottom housing part andhaving an end arranged at and facing an interior of the bottom housingpart (20 a); a housing associated fastening device (24) secured to thebottom housing part and within a radial interior of the bottom housingpart air-permeable cylindrical support body (21); wherein thecylindrical support body (21) cylindrically surrounds a radial exteriorof the air filter element (10); wherein the housing associated fasteningdevice (24) interacts with and engages with a filter-associatedfastening device (14) of the air filter element for fastening the airfilter element (10) by means of an insertion/rotation movement.
 12. Thefilter arrangement according to claim 11, wherein the filter element(10) is received completely and positively into the interior of thesupport body (21).
 13. The filter arrangement according to claim 11,further comprising a second cylindrical filter element (60) arranged onand encircling an exterior of the support body (21); wherein the supportbody (21) forms a central tube of the second cylindrical filter element(60).